1. Field of the Invention
The present invention generally relates to a shift device for a boat. More particularly, the present invention relates to a shift device for a boat in which movement of a shift mechanism is operated by an actuator as controlled by a remote shift lever, and a method of using the shift device.
2. Description of the Related Art
Conventionally, a transmission of a boat includes a dog clutch that changes the modes of transmission operation among at least one speed fore, one speed aft and neutral. The dog clutch is engaged and disengaged by a lever that is rotated with a push-and-pull cable. The cable is moved via a handle gear shift.
With such a conventional configuration, the boat operator directly operates the dog clutch. For proper operation, the boat operator must use a sufficient amount of force without attempting to over-finesse the transmission. For instance, if insufficient force is applied, the gears may grind during engagement or the gears may be difficult to disengage. Further, if too much force is applied, the shifting mechanism can be damaged.
Japanese Patent Application No. 10-184402 and Japanese Patent Application No. 2004-1638 both disclose shifting mechanisms similar to those described above. The first of these describes that the rotation of the shift lever is detected with a sensor, such as a clutch switch or a throttle adjusting mechanism. The detected signals are transmitted to a control unit. At the same time, the control unit, according to the detected signals, adjusts the power from a power source and transmits it to a throttle motor or a clutch motor. Therefore, it is possible to interconnect the control unit and the outboard motor engine through a signal line.
This patent application explains, however, that the remote control box and the engine are not necessarily interconnected through the push-and-pull cable having a high rigidity. Thus, when the outboard motor is turned during steering operations, the signal line, which has a low rigidity, follows well enough the turn of the outboard motor, which results in improvement in the quality of operation.
Japanese Patent Application No. 2004-1638 discloses a shift device for an outboard motor that has an internal combustion engine mounted in the upper part and a propeller in the lower part, which propeller is driven by the engine. The outboard motor is attached to the rear part of a hull to propel the hull forward and rearward. Gear shifting is performed by sliding a shift slider through a shift rod, wherein the shift rod is driven by an actuator located within the outboard motor.
Because the shift rod is moved by the actuator, which is located within the outboard motor, the available required force is smaller in comparison to manually driving the shift rod. Thus, there is an improved sense of control. Further, the connection structure between the shift rod and the actuator can be simplified relative to a structure in which the actuator is located on the hull of the boat. Thus, such a construction features fewer parts, has a lower weight and does not take up unnecessary space in the boat hull.
In the constructions described in both of these patent applications, the operator still has a perception in performance lag because of a perceived inadequate response of the actuator to the shift lever operation. That is, when the shift lever or the remote control lever is operated quickly, there is a delay in response. In addition, when the shift lever is operated slowly, for example, from the neutral to the forward position, the gear shift actually anticipates the completion of movement of the shift lever.
Therefore, a shift device for a boat is desired that makes it possible to improve shift operation quality by improving the responsiveness of the actuator to movement of the shift lever.